Project Summary An appropriate routing of information in the brain based on the current task demands is essential for successfully dealing with a complex, changing environment. Such routing mechanisms seem to be impaired in disorders like schizophrenia. Unfortunately, we currently do not understand how the brain is able to regulate the flow of information. A recent theory suggests that synchronous activity plays an important role. However, it is still fiercely debated in the neuroscience community whether synchronous activity and precise spike timing in cortex have a functional significance and, if so, what role they play. A major obstacle to answering these questions is the lack of suitable experimental techniques for artificially manipulating brain activity with a precise timing relationship to currently ongoing neural activity. Techniques that allow the experimental manipulation of neural activity play an instrumental role in establishing a causal link between brain activity and its functional significance. The goal of the proposed project is therefore to develop a closed-loop stimulation technique that allows the measurement of currently ongoing neural activity in the form of a local field potential, analyzes it in real time, and can trigger a stimulation device like, for example, electrical microstimulation or optogenetic stimulation in such a way that artificially injected neural activity is phase-locked to currently ongoing oscillations. This includes the development of an algorithm that reliably tracks the instantaneous phase of a dominant component of the local field potential as well as finding a suitable implementation of this algorithm for controlling a stimulator in real time. Making the proposed technology available to the scientific community is expected to provide major breakthroughs in understanding the functional significance of synchronous activity and precise spike timing in the brain.